The 24-year-old pop star made an appearance in fiancée Hailey Baldwin's Instagram Story on Wednesday night, giving us major Magnum P.I. vibes in a Hawaiian-print shirt and cap combo that looks like it was stolen straight off the set of the popular '80s crime series.

In the pic, Bieber leans against a doorway, looking off into the distance as Baldwin slyly snaps his photo. If you look closely, you can see that the singer is sporting a mustache again!

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Biebs' facial hair was on full display as he and Baldwin later stepped out for dinner at Mastro's Steakhouse in Beverly Hills, California. The 21-year-old model -- chic in a pink-and-white striped hoodie with white Dr. Martens boots -- was all smiles while holding hands with her future husband.

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A source tells ET that Bieber and Baldwin are enjoying their engagement, and although they're beyond excited to tie the knot, they are in no rush to get married or even plan their nuptials. Bieber is just happy to be Baldwin's beau as he's "always been in love" with her, says the source.

"After years of ups and downs, Justin took some time to evaluate everything in his life, took time off his tour [and] music and got to enjoy a more simple life. With that time, Justin knew he wanted to spend his time with Hailey and have a future with her," the source continues. "Hailey and Justin are enjoying summer and seeing their family and friends. Wedding planning hasn't really started other than talking about what the couple would like when they do tie the knot."